Twenty-two percent of Americans claim to be certain that Jesus will return to earth to judge the living and the dead sometime in the next fifty years. Another twenty-two percent believe that he is likely to do so. The problem that most interests me at this point, both scientifically and socially, is the problem of belief itself. What does it mean, at the level of the brain, to believe that a proposition is true? The difference between believing and disbelieving a statement—Your spouse is cheating on you; you've just won ten million dollars—is one of the most potent regulators of human behavior and emotion. The instant we accept a given representation of the world as true, it becomes the basis for further thought and action; rejected as false, it remains a string of words.

What I believe, though cannot yet prove, is that belief is a content-independent process. Which is to say that beliefs about God—to the degree that they are really believed—are the same as beliefs about numbers, penguins, tofu, or anything else. This is not to say that all of our representations of the world are acquired through language, or that all linguistic representations are on the same logical footing. And we know that different regions of the brain are involved in judging the truth-value of statements drawn from different content domains. What I do believe, however, is that the neural processes that govern the final acceptance of a statement as "true" rely on more fundamental, reward-related circuitry in our frontal lobes—probably the same regions that judge the pleasantness of tastes and odors. Truth may be beauty, and beauty truth, in more than a metaphorical sense. And false statements may, quite literally, disgust us.

Once the neurology of belief becomes clear, and it stands revealed as an all-purpose emotion arising in a wide variety of contexts (often without warrant), religious faith will be exposed for what it is: a humble species of terrestrial credulity. We will then have additional, scientific reasons to declare that mere feelings of conviction are not enough when it comes time to talk about the way the world is. The only thing that guarantees that (sufficiently complex) beliefs actually represent the world, are chains of evidence and argument linking them to the world. Only on matters of religious faith do sane men and women regularly dispute this fact. Apart from removing the principle reason we have found to kill one another, a revolution in our thinking about religious belief would clear the way for new approaches to ethics and spiritual experience. Both ethics and spirituality lie at the very heart of what is good about being human, but our thinking on both fronts has been shackled to the preposterous for millennia. Understanding belief at the level of the brain may hold the key to new insights into the nature of our minds, to new rules of discourse, and to new frontiers of human cooperation.